The contrabass clarinet and contra-alto clarinet are the two largest members of the clarinet family that are in common usage. Modern contrabass clarinets are pitched in BB♭, sounding two octaves lower than the common B♭ soprano clarinet and one octave lower than the B♭ bass clarinet. Some contrabass clarinet models have a range extending down to low (written) E♭, while others can play down to low D or further to low C.
The contrabass clarinet is also sometimes known by the name pedal clarinet, this term referring not to any aspect of the instrument’s mechanism but to an analogy between its very low tones and the pedal tones of the trombone, or the pedal division of the organ.
This is a very impressive instrument. The size alone is fantastic not to mention the sound that it can produce.
Here is a piccolo and a contrabass clarinet duet:
Octocontralto & Contrabass Clarinet Duet